Charge Carrier Modulation in Low Dimensional Semiconductors
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Bismuth sulfide (Bi2S3) nanowires have their transfer characteristics in a backgated transistor geometry analyzed with accompanying resistance noise spectroscopy data. The ON/OFF ratio, mobility and activation energy are extracted which reveal the presence of a previously theorized midgap state originating from native sulfur vacancies. This has a broad impact for all sulfide nanostructured materials and open new avenues for a defect-engineering route to explore material properties and functionalities. Vanadium pentoxide bronzes (MxV2O5) are made from intercalating guest atoms into the structure of V2O5. This gives an otherwise standard semiconductor system vast new possibilities such as metal-insulator, superconducting and charge ordering transitions. The growth parameters allow for these bronzes to form an abundance of phases ranging from long tunnel networks to layered arrangements which give the ever growing list of 2D materials a new family member. Herein two phases of hydrated nickel intercalated V2O5, delta and sigma, are shown to have an intrinsic memory feature in their current-voltage characteristics due to hydration, donating a mobile proton in the interlayer channel. This memory feature is characterized by testing its stability over time (retention) and cycle (endurance). This work is just the beginning in what could potentially be the discovery of an entirely new type of memory seen in oxides.Cuproiridsite (CuIr2S4) is a strongly correlated electron system. These systems have electronic behavior that deviate from typical band structure calculations unless the interaction between the electrons are taken into account. CuIr2S4 is a 5d electron system exhibiting a structural and metal-insulator transition at 230 K. Aside from observing this transition thermally, while in the insulating phase an electric field can be applied to drive the sample into its metallic phase. The thermal and electrically driven transition are studied for their physical mechanism.